Rename library/ecp_alt.h to ecp_internal_alt.h

library/ecp_alt.h (declaring individual functions of the ECP module that can
be substituted, included when building the library with
MBEDTLS_ECP_INTERNAL_ALT enabled) clashes with ecp_alt.h (not provided,
declaring types of the ECP module when the whole implementation is
substituted, included when building the library with MBEDTLS_ECP_ALT enabled).
Depending on the search path during build, this can make MBEDTLS_ECP_ALT
unusable.

Rename library/ecp_alt.h to follow the naming convention of other alt headers:
MBEDTLS_XXX_ALT corresponds to xxx_alt.h.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog b/ChangeLog
index dc6e451..ddaf3fd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,7 +22,7 @@
      Various helpers and definitions available for use in alt implementations
      have been moved out of the include/ directory and into the library/
      directory. The files concerned are ecp_internal.h and rsa_internal.h
-     which have also been renamed to ecp_alt.h and rsa_alt_helpers.h
+     which have also been renamed to ecp_internal_alt.h and rsa_alt_helpers.h
      respectively.
    * Move internal headers.
      Header files that were only meant for the library's internal use and
diff --git a/docs/3.0-migration-guide.md b/docs/3.0-migration-guide.md
index 2d031c6..a4a59b8 100644
--- a/docs/3.0-migration-guide.md
+++ b/docs/3.0-migration-guide.md
@@ -59,7 +59,7 @@
 If you're providing alt implementations of ECP or RSA, you'll need to add our
 `library` directory to your include path when building your alt
 implementations, and note that `ecp_internal.h` and `rsa_internal.h` have been
-renamed to `ecp_alt.h` and `rsa_alt_helpers.h` respectively.
+renamed to `ecp_internal_alt.h` and `rsa_alt_helpers.h` respectively.
 
 If you're a library user and used to rely on having access to a structure or
 function that's now in a private header, please reach out on the mailing list
diff --git a/library/ecp.c b/library/ecp.c
index f450056..044bbe1 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -99,7 +99,7 @@
 #define mbedtls_free       free
 #endif
 
-#include "ecp_alt.h"
+#include "ecp_internal_alt.h"
 
 #if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
 #if defined(MBEDTLS_HMAC_DRBG_C)
diff --git a/library/ecp_alt.h b/library/ecp_internal_alt.h
similarity index 99%
rename from library/ecp_alt.h
rename to library/ecp_internal_alt.h
index 6b1b29f..9b157ea 100644
--- a/library/ecp_alt.h
+++ b/library/ecp_internal_alt.h
@@ -1,5 +1,5 @@
 /**
- * \file ecp_alt.h
+ * \file ecp_internal_alt.h
  *
  * \brief Function declarations for alternative implementation of elliptic curve
  * point arithmetic.
@@ -293,5 +293,5 @@
 
 #endif /* MBEDTLS_ECP_INTERNAL_ALT */
 
-#endif /* ecp_alt.h */
+#endif /* ecp_internal_alt.h */